Test Details: The insulin fasting test measures the levels of insulin in blood after a fasting period of 8 hours. Insulin is a hormone secreted by the beta cells of the pancreas and helps in maintaining normal blood glucose levels. This test is used as an adjunct in the diagnosis of diabetes and insulin resistance. Insulin stimulates the uptake of glucose by cells, leading to a fall in blood glucose, and insulin levels in turn. Disruptions in this mechanism due to low insulin production by pancreas or inability of cells to respond to insulin (insulin resistance) cause a rise in blood sugar levels or hyperglycemia. Fasting insulin outside the normal range could indicate diseases such as type 1 or type 2 diabetes.